The present disclosure relates to an image forming apparatus including a cleaning blade removing waste toner remained on an image carrier carrying a toner image.
Conventionally, an image forming apparatus of an electrographic manner, such as a printer or a copying machine, includes an image carrier, such as a photosensitive drum, having a surface carrying a toner image. In addition, the image forming apparatus includes a developing device developing the toner image onto the image carrier and a transferring device transferring the toner image on the image carrier onto a recording medium, such as a sheet. Further, the image forming apparatus includes a cleaning device removing waste toner remained on the image carrier after transferring and a waste toner box collecting removed waste toner. The cleaning device includes a cleaning blade removing waste toner from the surface of the image carrier.
The cleaning blade is arranged so that its blade edge comes into contact with the surface of the image carrier in a counter direction to a rotating direction of the image carrier. When the image carrier is rotated, by lubricity of an eternal additive of the waste toner on the image carrier, a stick-slip phenomenon of the cleaning blade to the image carrier is restrained. Therefore, if the eternal additive is exhausted, frictional force between the cleaning blade and the surface of the image carrier is increased, balance of the stick-slip phenomenon is lost, and blade turning-up may be caused so that the cleaning blade is turned up in an opposite direction to the counter direction. It is feared that image failure is caused due to the blade turning-up. In order to restrain the blade turning-up, in the image forming apparatus, toner placing (turning-up restraining process) may be carried out so as to feed toner from the developing device to the image carrier.
As an example, the image forming apparatus includes a photosensitive body (photoreceptor) unit for each color including an image carrier cleaning blade cleaning transfer residual toner (waste toner) remained on a photosensitive drum (image carrier) after transferring and a collected toner container (waste toner box) collecting the transfer residual toner. In addition, the image forming apparatus includes an intermediate transferring body cleaning blade cleaning transfer residual toner remained on an intermediate transferring belt to form a blade rolling-up prevention pattern on a non-image area of the photosensitive drum by a developing roller and to provide the blade rolling-up prevention pattern to the intermediate transferring body cleaning blade. Subsequently, the image forming apparatus includes a filling rate detecting means detecting a rate of the transfer residual toner collected in the collected toner container to a capacity of the collected toner container and to select a color, of which the filling rate of the collected toner container detected by the filling rate detecting means is smallest, as a color used for the blade rolling-up prevention pattern.
The above-mentioned blade turning-up of the cleaning blade is easily caused at an end in a rotation axis direction of the image carrier (a width direction of the recording medium). Incidentally, in the image forming apparatus, in a case where the recording medium has a width corresponding a maximum sheet passing area in the rotation axis direction of the image carrier (e.g. A4 size), the toner image is formed to the vicinity of the end in the rotation axis direction of the image carrier. However, in a case where the recording medium has a correctively narrow width (e.g. a small size, such as A5 size), such as a width equal to or less than a half of the maximum sheet passing area, the toner image is not formed at the vicinity of the end in the rotation axis direction of the image carrier. Therefore, if a proportion of image forming for recording media of the small size becomes high, an amount of the waste toner at the vicinity of the end in the rotation axis direction of the image carrier is decreased and the blade turning-up is easily caused.
Incidentally, if a constant toner is always fed to a non-image forming area of the image carrier, toner consumption is increased regardless of a size of the recording medium. At this time, there are problems that usage efficiency is lowered and that the waste toner box is filled for a short period. If the waste toner box is enclosed with a toner container, the waste toner box is preferably replaced when the toner container is replaced. However, if toner consumption is increased due to restraining of the blade turning-up, the waste toner box may be filled before the toner container is utilized to the fullest. At this time, because it is necessary to prepare and replace a new waste toner box, a cost load and a work load are caused for a user and an unusable state of the image forming apparatus is caused due to replacement of the waste toner box.